Over the last decade many researchers have turned much attention to the vaccine against Lyme disease as the only effective preventive method. Recently two groups of researchers have published data on their trials carried out on humans. The vaccine given to volunteers consisted of recombinant outer surface protein (Osp)A. A two-year observation of the persons studies revealed that 79% of them had developed resistance to Borrelia burgdorferi infection. These data were evaluated by the FDA experts who recommended the vaccine for general use with the following reservations that have to be elucidated: too short observation of vaccinated persons, no possibility to vaccinate children and the problem of vaccinating people with undiagnosed Lyme disease.